Grey Subs when converting 10bit HDR to 8bit SDR

[lordcamel]

Hello,

I have been playing around with the Vapoursynth-> Color-> HDR to SDR filters because I wanted to test converting 10bit to 8bit.

I have tested the HDR10ToSDR filter and it works ok but it makes the encode take a very long time.

I have tested the libplacebo filter and it works very well and the encode times are very good.

I have a problem with both though, and I do not know how to fix it. The problem is that when I use either of these filters the subtitles turn from white to grey.

I made an image to show what I am talking about

https://drive.google.com/file/d/1DoWiGGM...sp=sharing

You can see that the colors are still a bit off too, I haven't had the best experience with HDR to SDR.

I am using x264 to encode the video. 

Both the HDR10ToSDR filter and libplacebo produce an 8bit video with slightly off colors. I guess that's a limitation of the conversion process though.

Anyway, any advice or help anyone could offer me would be appreciated, I want to learn more regardless.

My main goal is just to fix the grey subs but if anyone thinks they could help me get better colors in my encoded 8bit video, that would also be nice.

Running latest experimental version 26.06.29.1 on Windows 11

I apologize if I left any details out, this is my first post and I am not sure how to fully document everything.

Regards,

lordcamel

[lordcamel]

The subs are .sup files. I guess they contain some info on the color grading and when they are muxed with an 8bit video they display incorrectly.

[lordcamel]

OK,

so after a little more research, I think I found the problem. As far as I can tell it's completely unrelated to Hybrid, so sorry for posting about it.

Seems like these .sup files contain PGS subs that are bitmap based and essentially, the subtitles look correct in HDR but too dark in SDR because the tone mapping that normally brightens them is absent or handled differently. 

Anyway. That's that

All the best.